1. Field
One or more embodiments relate to a method of sensing connection of a USB device by an image forming apparatus in a power save mode.
2. Description of the Related Art
Recently, as the concept of power saving has become increasingly important, methods of saving standby power of electric appliances are being introduced. In the case of an image forming apparatus, standby power may be saved by turning off some internal components of the image forming apparatus by entering a power save mode when an operation, such as printing, is not being performed.
Furthermore, a recent image forming apparatus may include a universal serial bus (USB) port, and may be connected to other external devices and transmit and receive data. In this regard, the image forming apparatus may include a USB device controller for controlling the image forming apparatus to operate as a USB device, and includes a USB host controller for controlling the image forming apparatus to operate as a USB host.
When the image forming apparatus operates as a USB device, the image forming apparatus is supplied power from a device that is connected to the image forming apparatus and operates as a USB host. Hence, when the image forming apparatus is in a power save mode, even though the USB device control is in an off state, if a device operating as a USB host is connected to the image forming apparatus, the supplied power may be sensed, and the USB device controller may be woken up.
However, when the image forming apparatus operates as a USB host, the image forming device supplies power to a device that is connected to the image forming apparatus and operates as a USB device, via a voltage bus (VBUS) line, and thus wake-up by power sensing is impossible. Hence, according to the conventional art, even if the image forming apparatus enters a power save mode, there is a limitation in saving standby power by using a method of maintaining an on state without turning off the USB host controller or by using a method of first turning off the USB host controller and then checking whether a USB device has been connected by periodically turning on the USB host controller.